That the money of account of the United States shall be expressed in dollars or units, dismes or tenths, cents or hundredths, and milles or thousandths, a disme being the tenth part of a dollar, a cent the hundredth part of a dollar, a mille the thousandth part of a dollar, and that all accounts in the public offices and all proceedings in the courts of the United States shall be kept and had in conformity to this regulation.[3]

The mint of Philadelphia made half cents worth 5 mills each from 1793 to 1857.

Tokens in this denomination were issued by some states and local governments (and by some private interests) for such uses as payment of sales tax.[4] These were of inexpensive material such as tin, aluminium, plastic or paper. Rising inflation depreciated the value of these tokens in relation to the value of their constituent materials; this depreciation led to their eventual abandonment. Virtually none were made after the 1960s.

Today, most Americans would refer to fractions of a cent rather than mills, a term which is widely unknown. For example, a gasoline price of $3.019 per gallon, if pronounced in full, would be "three dollars (and) one and nine-tenths cents". Discount coupons, such as those for grocery items, usually include in their fine print a statement such as "Cash value less than 1⁄10 of 1 cent." There are also common occurrences of "half-cent" discounts on goods bought in quantity. However, the term "mill" is still used when discussing billing in the electric power industry as shorthand for the lengthier "1⁄1000 of a dollar per kilowatt hour". The term is also commonly used when discussing stock prices, the issuance of founder's stock of a company, and cigarette taxes.

Property tax

Property taxes are also expressed in terms of mills per dollar assessed (a mill levy, known more widely in the US as a "mill rate"). For instance, with a millage rate of 2.8 mills, a house with an assessment of $100,000 would be taxed (2.8 × 100,000) = 280,000 mills, or $280.00. The term is often spelled "mil" when used in this context.[5]

Finance

The term mill is often used in finance, particularly in conjunction with equity market microstructure, as one-hundredth of a cent. For example, a broker that charges 5 mils per share is taking in $5 every 10,000 shares traded. Additionally, in finance the term is spelled "mil".[6]

Some exchanges allow prices to be accounted in ten-thousandths of a dollar ($29.4125, for example). This last digit is sometimes called a "decimill" or "deci-mill", but no exchange officially recognizes the term.

Canada

Mills are or were formerly used in some cities to express property tax rates, in the same manner as in the U.S.

United Kingdom

Proposed on several occasions as a division of the British pound under the "Pound and Mil" system, the mill was occasionally used in accounting. The 1862 report from the Select Committee on Weights and Measures[7] noted that the Equitable Insurance Company had been keeping accounts in mills (rather than in shillings and pence) for such purposes for over 100 years. Such a unit of a thousandth of a pound would have been similar in value to the then-existing farthing coin (1⁄960 of a pound).

Malta

Maltese lira coinage included 2 mil, 3 mil, and 5 mil coins from 1972 to 1994, with 10 mils being equal to one cent. Prices could still be marked using mils until the country switched to the euro in 2008, however these were then rounded up for accounting purposes.

Republic of Rose Island

The short-lived and unrecognized Republic of Rose Island (a micronation off the Italian coast) had the mill as its official currency (milo in the official language Esperanto).

Hong Kong

Between 1863 and 1866 the mill coin was the lowest denomination issued by the British government in Hong Kong; it was eliminated due to its unpopularity.[8]

Cyprus

The mill was used with the Cypriot pound, starting with decimalization in 1955, and lasting until 1983. However, coins smaller than 5 mils were not used since the mid 1960s. When switched to cents in 1983, a ½-cent coin was struck that was abolished a few years later.

Tunisia

To this date[when?] 1, 2, and 5 millime (mills) are still in circulation, but they are no longer issued by the central bank. However, larger coins such as the 10, 20, 50, and 100 millime coins are still in use and production.